When a firearm is discharged, gases generated by combustion of an explosive mixture in the firearm chamber propel a projectile through the firearm barrel and out the muzzle. These propellant gases exit the muzzle in the wake of the projectile and mix with the ambient air. The exiting gases cause or contribute to three unwanted effects: muzzle flash, recoil/muzzle lift and interference with projectile stability.
Muzzle flash occurs as a result of the contact of the propellant with the air at the muzzle. The propellant gas mixture, containing traces of unburned powder, remains extremely hot at the end of the barrel. Oxygen in the surrounding air combines with the hot gas to enable combustion of the residual chemicals, resulting in a visible flash of light just beyond the end of the barrel. Muzzle flash is undesirable because it gives away the location of a shooter at night or under other low ambient light conditions.
Recoil is the reactive force against the gun barrel applied by the moving bullet and propellant. A substantial component of this reactive force is created by the forward ejection of the propellant out the muzzle. The recoil force is applied at a point above the center of gravity of the firearm and this, combined with the torque reaction generated by the rapidly spinning projectile, tends to pull the muzzle upward and to the right upon firing.
Projectile stability is affected by the exiting propellant gas that passes and surrounds the projectile immediately beyond the muzzle. The velocity of the propellant is roughly twice the velocity of the projectile, so that at exit some propellant moves around and in front of the projectile. The propellant immediately slows down in the air, causing drag on the projectile. More significantly, in the case of a firearm with a rifled barrel, the propellant exerts a force that makes the spinning projectile wobble or "yaw", thereby causing the projectile to take longer to stabilize and decreasing the accuracy of the firearm.
A number of approaches to suppressing or hiding muzzle flash, alone or in combination with lessening recoil, appear in the prior art. In U.S. Pat. No. 4,024,791, for example, a barrel extension with rear-angled holes is employed to draw ambient air into the barrel behind the moving projectile to cool the propellant gas so that combustion at the exit point is reduced or eliminated. The same patent also features adding longitudinal baffles inside the barrel extension to permit expansion and resultant additional cooling of the propellant gases before exit.
The standard, government-issue flash hider used on military automatic and semi-automatic weapons such as the AR-15 and M-16 is illustrated in U.S. Pat. No. 5,092,223 for a muzzle brake that may be utilized in connection with the flash hider. The government-issue flash hider is of the "bird cage" type, designed with a conical, expanding internal diameter barrel extension with slotted longitudinal openings along part of its length. The propellant gases expand (thereby cooling) in the hider barrel, and exit the longitudinal slots. Unfortunately, sufficient heat and pressure remain to permit visible combustion and flash.
U.S. Pat. No. 4,570,529 also employs a "bird cage" design, but adds a length of smoothbore barrel between the weapon and the "bird cage" to elongate the moving bullet and provide further burn time for the propellant. An improvement, shown in U.S. Pat. No. 5,005,463 changes the "bird cage" to a pair of diametrically opposed vent slots, creating a pair of furcations, each of which has at least one radially directed vent opening. A flash suppressor design available on the market is made up of a barrel extension with three straight prongs, leaving open slots between the prongs. These designs result in some suppression of muzzle flash, but leave more residual flash than is desirable.